The Jarrettsville plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
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16° on Nov. 16, 1996, the coldest reading for this week of the year since 1988. Next is 17° in 2017.
Jarrettsville’s center stands about 620 ft above sea level. Within three miles the land runs from 430 ft to 750 ft, a difference of 320 ft: rolling country. The highest named summit within 15 miles is Spook Hill, about 850 ft, 13 miles west.
Under the town center the state geologic map shows Wissahickon Formation; Lower Pelitic Schist (biotite-schist), from the Proterozoic, 542 to 2,500 million years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 28×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Biotite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 15 mi of the line.
Gabbro. Age: Proterozoic to Paleozoic, 252 to 2,500 million years old. About 3 mi of the line.
Muscovite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 3 mi of the line.
Muscovite-gneiss. Age: Proterozoic, 542 to 2,500 million years old. About 2 mi of the line.
Gabbro, quartz-diorite. Age: Paleozoic, 252 to 542 million years old. About 1 mi of the line.
Gneiss. Age: Paleozoic, 252 to 542 million years old. About 0.4 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Jarrettsville reaches Chesapeake Bay and the Atlantic Ocean by way of East Branch Winters Run, Winters Run, Otter Point Creek and the Bush: about 30 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Jarrettsville; river miles along the main stem, rounded.
Jarrettsville has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 24° in January. A normal year brings about 34 inches of snow; with the rain, that comes to about 48 inches of water.
On November 14 Jarrettsville normally reaches 54° and falls to 36°. The record high is 73°, in 1993; the record low 22°, in 2019. The most rain on this date, 1.59 in, fell in 1995.
Normals 1991–2020 and records since 1988 at Millers 4 NE, 19 miles west-northwest, 240 ft higher. NOAA, through RCC-ACIS.
